Radiosignaling call system



Dem 4,1923.

RADIOS IGNALINQ CALL SYSTEM Filed Aug. 18. 1922 2 Sheets-Sheet 1 :P I 5 I l 56 I L E J l I I m l I /71 I 4 A 3), 1 I 1 41 t l c pig T INVENTOR. 4 ZflfiTJ/Zmim/ Dec. 4 1923. 1,476,003

DE Loss K. MARTIN RADIOSIGNALING CALL SYSTEM Filed Aug. 18. 1922 2 Sheets-Sheet 2 E\ ,fi'

*2; $6 Q, 0 0; 2 5 I 1 F9 1 I INVENTOR.

ATTORNEY Patented Dec. 4, 1923.

UNITED STATES 1,476,003 PATENT OFFICE.-

nn LOSS x. mun, or ORANGE, NEW JERSEY, nssrenon 'ro AMERICAN" TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION or new YORK.-

RADIOSIGNALING CALL SYSTEM.

Application filed August 18, 1922. Serial 110.682,?29.

To all whom it may concern:

Be it known that 1, DE Loss K. MARTIN, residing at Orange, in the county of Essex and State of New Jersey, have invented certain Improvements in tadiosignaling Call Systems, of which the following is a specification.

This invention relates to a radio slgnal call system and more particularly to the association of a central radio station with a number of remote stations. Its object is to provide circuits to facilitate calling any one of the remote stations and to permit such stations to call the central station, giving information at the same time as to which remote station is calling. A further object is to make provision for communication with a very large number of outlying stations by a simple calling arrangement. To this latter end I use certain ringing frequencies, preferably voice frequencies, impressed on the carrier, and by various combinations of these frequencies a comparatively few ringers, with suitable selective devices, will make prfivision for a relatively large number of ca s.

Still a further object of my invention is to provide a circuit which, by its symmetry,

will permit an indefinite expansion of the system to provide for additional remote stations.

The system will find particular application in such signaling as between harbor tubs, river-craft and a shore station, or from airplanes to an aid-field station, or from point to point over land. For such service the distances over which operation will take lace will normally be relatively short and therefore it will probably be desirable to use the higher range of radio frequencies, which will naturally allow a greater number of communications to be established. It may be that the stations of one interest, as represented by one central station, may communicate with its various outlying stations on one radio carrier, using, however, different combinations of voice or other frequencies for selective signaling. On the other hand, it may be that one central station will use a plurality of carrier frequencies, one for each outlying station, or one for each group of outlying stations. latitude of variation is possible, as will appear later. The system, as will also appear later, is somewhat analogous to awire tele- In this manner a wide.

phone system centering in an exchange in which there is a plurality of channels corresponding to each pair of outgoin wires and in which each pair of wires may be a party line, the correct party being obtained by means of selective ringing.

The invention will be better understood by reference to the accompanying drawmg, in which Figure 1 shows a circuit arrangement comprising my invention and adapted, for the sake of simplicity, to accommodate a few stations only. Fig. 2 shows a form of circuit arrangement which may be used at one of the remote stations, and Fig. 3 shows schematically an amplification of the circuit of Fig. 1, indicating how that circuit may be expanded to accommodate a larger number of remote stations.

Referring particularly to Fig. 1, there are shown two receiving circuits, R, and R and a transmitting station T. Withthe receiving station R is associated a switching mechanism S comprising a plurality of contact points which may be operated to produce one efiect or another. A similar switching mechanism S is associated with the receiver R At the same time these switching mechanisms are associated with the transmitter T, with a talking circuit L and a ringing control circuit P.

While the switches S and S which are shown as identical in structure, may take on a variety of forms, in the drawing they are shown as possessing on the one side 12 contacts or terminals represented by the numerals 1 to 12 respectively and having on the other side a switch with four contacts or terminals represented by the numerals 13 to 16 respectively. Associated with this second side of the switches are a plurality of oscillators, O O 0 and 0 which may be of any suitable type, such as vacuum tube oscillators or mechanical vibrators. These oscillators are preferably of voice frequency and, taken in various combinations, are used as calling signals.

The transmitting station comprises an antenna 20 and a local circuit 21, this latter comprising a generator of carrier oscillations and suitable apparatus associated therewith, whereby these carrier oscillations may be modulated by a signal impressed thereon. The apparatus may-be associated 22, one coil of which is shown as the inductance of the antenna. Two relays 24 and 25 are provided, upon the operation of which a greater or smaller amount of inductance may be included in the antenna circuit, thus changing the frequency to which this 'antenna is tuned.

The receiving circuit R, comprises an antenna, which is here shown, as the loop antenna 30 with an associ a-tcd condenser 31. Across this antenna is connected suitable receiving mechanism 32, comprising in general a detector and such amplifiers as may be necessary. The output of this circuit 32, as shown in the receiver R is normally connected with a selector circuit 34, which upon receipt of a proper combination of impulses, will operate an indicating means such as a lamp 33. Contacts from the circuit 32 to the selector 34 are'controlled by a relay 35. upon operation of which connection with the selector 34 is broken and contact is made through con ductors 36 to a line L, overwhich a message is to be rendered. The connection to the line-L is preferably through a connection M comprising a hybrid coil and a balancing network N, in order that speech coming from the line L shall not enter into the receivers but may be taken off for transmission over the the various contacts 2 to 10 of the switches 3 and S connected to corresponding leads,

indicated by 2' to 10. If aremotestation, corresponding to the receiver R sends in a call consisting of a radio carrier corresponding to the loop antenna 30 and modulated with respect to certain voice frequencies f, and 7''}, the receipt and detection of such a calling signal will operate the lamp 33 through the selector mechanism 8 l-Vhen the operator observes this signal he throws the lever of the switch S, to the answering position. A circuit will then be closed through the battery 38, conductor 2', contacts 2 and 1 and relay 35 to ground. This will disconnect the selector s and connect the receiver circuit 32 through the conductors 39 to one pair of terminals of the hybrid coil M, whence the message goes to the telephone receiver of the operator or subscriber. The same operation of the switch S, by closing the contacts 4 and 5 and the contacts 8 and 9 connects the conjugate points of the hybrid coil M to the transmitter in the following manner for the purpose of enabling duplex conversation: line L, conductor 40, lead 4, contacts 4 and 5, lead 5', conductor 44, transmit-ting apparatus 21, conductor 45, lead 8, contacts 8 .and-9, lead 9, conductor 41 and line L. At the same time the operation of the switch makes connection between contacts 11 and 12, thus closing circuit through battery 46, conductor 10, contacts 12 and 11, cbnductor 47 and relay 24 to ground. The closing of this c1r cuit, attracting the armature of 24, connects the antenna 20 through a portion of the inductance of the transformer 22, whereby the antenna is tuned for that frequency which corresponds t-o't-he station from whence a message came to the receiver R. A complete talking channel between the two stations is thus established and upon the com-- pletion of the conversation the switch S, is returned to its normal position, the various contacts thenbeing related as shown in S In case a message from a station corresponding. to the receiver It, were to arrive there would be impressed on the incoming carr er signahng impulses corresponding to frequencies f, and f which would operate on the selector 8 to give an indication at 33. The switch S would then bebrought to its answering position and circuits would be closed again in a similar manner to establish a talking channel In this case, the relay 25 through the conductor 48 would be operated to tune the antenna 20 to the corresponding frequency for this channel.

In case a call is to be initiated from the central station, use is made of the oscillators O 0 etc, to modulate the transmitted waves accordingly. If, for example, the station corresponding to the receiver R, is to be called the lever ofthe switch S, is turned to the left or ringing'p'osition. In this event the spring leads of the cont-acts 14 and 15 are separated to make connection with the contacts 13 and 16. At the same time the sprin members on the other side of the switci are brought together so that the spring members 2, 5, 8 and 11 make connection respectively with the contacts 3, 6, 7 and 10. By this operation, circuit is closed from the ground through the oscillator 0 contacts 13 and 14 and through the condenser 50 and the inductance 51, which latter is adapted to be connected to'gronnd by a Vibrating contact 55 of a relay 56. Also,

contact is made from ground through the oscillator O contacts 16 and 15, to a circuit comprising capacity 52 and inductance 53,

-which is also adapted for connection to ground through the vibrating element Associated with the inductances 51 and 53 are inductances 54. The bringing together of the sprin members on the right-hand side of the switc 1 S, has brought about the following conditions: circuit is closed through battery 38, lead 2', contacts 2 and lead 3', relay 56 and ground. This latter causes the vibrator 55 to alternately connect the inductances 51 and 53 to ground so that there is impressed on the coil 54 alternately alternating currents f corresponding to the oscillator 0 and f corresponding to the loo oscillator Circuit has at-the same time been closed from the transmitter circuit 21, through conductor 44, lead 5', contacts 5 and 6, lead 6', coil 54, lead 7 contacts 7 and 8, lead 8' and conductor 45 to the transmitter circuit 21. Circuit has also been closed through battery 46, lead 10', contacts 10 and the calling signal for that station which corresponds with the receiver R In the meantime, all connections with the talking circuit L and with the receiver R- have been interrupted. I

Upon receipt of the message at the remote station, an answering calling signal is sent out, which-operates the indicator 33 at the station R and the lever of the switch S is then brought to answering position, whereupon a telephone channel would be established between the line L and the remote station as explained heretofore.

' While the circuit at the remote station may take on a variety of forms, I have tral station. Referring to said Fig. 2, there is shown the antenna 60, which may be used both for transmission and reception. The transmitting apparatus 61 is associated with the antenna by means of the coils 62 and 63, the transmittin apparatus 61 comprising a generator 0 oscillations and a suitable modulator therefor. With this circuit 61 is associated a switch 65, by means of which either a selective ringer 66 or microphone 67 may be connected to control the modulator of the transmitter 61. In sending out a call, the spring members of the switch would be separated to connect in the selective ringer, which selective ringer might comprise suitable mechanical vibrators. Upon establishment of the talking channel, the switch may then be operated to disconnect the ringer 66 and connect the microphone 67. For purposes of receiving there is shown associated with the antenna 60 an inductance 70 and con denser 71 arranged in parallel and preferably tuned to a frequency equal to the transmitted frequency, and constituting thereby an anti-resonant circuit. The circuit also includes a demodulating device 72, a filter 73 and a detector amplifier 74.

Incoming signals of carrier frequency F readily pass through the anti-resonant circuit into the demodulator 72. At the same time the anti-resonant circuit suppresses almost wholly the transmitting carrier frequency F permitting, however, a. small portion to enter into the demodulator 72. Asa result there is produced an intermediate frequency F F this intermediate frequency being, of course, modulated with whatever si als wereimpressed upon the carrier F he band filter 73 may be inserted to pass the frequency F F with its modulated side bands. amplifier 74 will then yield the desired signal. There is associated with the detector amplifier 74 a switch 75, which normally closes, by contacts 76 and 77, a circuit through the selector 78. Upon receipt of the proper signaling impulses this selector will cause an indication at 79. By operation of the switch. 75, this selector is then cut out and the receiver 79 inserted in its place.

While I have shown and described in Fig. 1, mechanism for two remote stations, it is apparent from the symmetry of the circuit arrangement that a larger number of remote stations may be accommodated. This is illustrated by skeleton circuit drawing in Fig.

.3, in which there are shown switches S to S of the form described above and corresponding to seven remote stations and the indication that there may be other switches. Each of these would be connected to a corresponding receiving circuit, although it is not necessary that there should be a separate receiving antenna for each remote station. In the figure, I have shown but three such receiving circuits. Of these, R is shown as connected to the switching mechanism-S and S R is connected to the switches S S and S,. It, is connected to the switches S and S In case one receiving circuit is to be used for two or more remote stations, there should be suitable selective mechanism to indicate which re The detector shown as 'havingassociated with it selectors s and s and so with the other receivers. The transmitter T is shown as being adapted for three carrier frequencies by means of relays as described in connection with Fig. 1. Each relay may be associated with a suitable number of the switches- S. In this case,

for example, I have shown the switches S,

and S as connected to one relay 80, the switches S S and 8,, as connected with the relay 81 and the switches S and S asthe frequencies received and transmitted at any one remote station shall be different from that at other stations. The system of combinations of ringing impulses to accommodate the remote stations.

It may be that at the central station it will be desirable to have more than one operator and vfor this purpose a plurality of talking lines L should be provided. Fig. 3

shows two such lines, L and L with their corresponding hybrid coils and networks M, and M these being associated with the receivers and the switching mechanism in the manner indicated in connection with Fig. 1. The figure shows the coil M, connected to receivers R, and It, and the coil M connected to the receivers R, but any, other grouping may be used.

The connections between the switches, the oscillators and the receivers, the transmitter and the talking lines are in skeleton form only, it being understood that in gencral the circuit arrangement for each switch is identical to that of Fig. 1, and that by virtue of the symmetry, the circuit of Fig. 3 may be expanded indefinitely.

What is claimed is:

1. In a radio signaling system, a station adapted for communication with a plurality, of remote stations, and comprising a receiving circuit for each station with which communication is to be held, and a telephone and calling means for each such receiv-ing circuit selectively responsive to a call from a correspondin station only.

2. In a-ra io signaling system, a station adapted for communication with a plurality ofremote stations, and comprising a receiving circuit for each station with which communication is to be held, calling means for the receiving circuits each selectively responsive to a call from a corresponding station only, and switching mechanism associ ated with the first named station whereby a communication channel may be established with the calling station.

3. In a radio signaling system, a station adapted for communication with a plurality of remote stations, and comprising a receiving circuit for each station with which communication is to be held, a telephone and calling means for the receiving circuits each selectively responsive to a call from a corof the responding receiver and connecting the telephone thereto. 1

4. In a radio signaling system, a central station comprising a transmitting circuit and a plurality of receivin'g circuits adapted for communication with a plurality of re mote stations, calling means for selectively calling any remote station, switching mechanism at the central station for controlling the calling means and for connecting in the corresponding receiving circuit.

5. In a radio signaling system, a. central station comprising a transmitting circuit and aplurality of receiving circuits ada ted for communication with a plurality 0 remote stations, calling means for each receiving circuit selectively responsive to a call from a corresponding remote station only, calling means for selectively calling any remote station and switching mechanism at the central station for controlling said last calling means, and for connecting in the corresponding receiving circuit.

6. In a radio signaling system, a plurality of stations arranged for intercommunication, calling means for establishing channels between one station and any other station, comprising apparatus responsive to a plurality of different combinations of voice frequencies on a. given carrier frequency.

7 Ina radio signalin system, a plurality of stations arranged tbr intercommunication, calling means for establishing channels between one station and any other, comprising a given combination of voice frequencies on a plurality of different carrier frequencies".

8. In a radio signalinf system, a plurality of stations arranged or intercommunica tion, calling means for establishing channels between one station and any other, comprising apparatus responsive to a plurality of different. combinations of voice frequencies on a given carrier frequency and a given combination of voice frequencies on a plurality' of different carrier frequencies.

In testimony whereof, I have signed my name to this specification this 14th day of August 1922.

DE LOSS K. MAR-TIN. 

